Chemistry - Ionic Equilibrium Question with Solution | TestHub

Concentration of ${\mathrm{NH}}_4\mathrm{OH}$ solution $=0.1\mathrm{N}$ Concentration of ${\mathrm{OH}}^{-}$ions in solution, $$\begin{array}{rl}\left[{\mathrm{OH}}^{-}\right]=20\%\text{ of }0.1\mathrm{N}& =\frac{20}{100}\times 0.1\\ & =0.02\mathrm{N}\end{array}$$ $$\begin{array}{rlrl}\Rightarrow \mathrm{pOH}=-\log \left[{\mathrm{OH}}^{-}\right]& =-\log (0.02)& & \\ & =2-0.301=1.699& & \\ \Rightarrow & & \mathrm{pH}=14-\mathrm{pOH}& =12.30\end{array}$$